The present invention relates to a facility and a method for producing hydrocarbon. The present invention also relates to a method for upgrading a hydrocarbon production facility.
In the field of hydrocarbon production, it is known to use the injection of pressurized gas into a hydrocarbon production well to improve the production of this well. Documents EP 0 756 065 A1 and FR 2 783 557 A1, for example, describe the injection of gas for activation of the hydrocarbon production of a well. Gas injection reduces the hydrostatic pressure of the well to facilitate the extraction of hydrocarbons. However, such method known by activation using gas injection (method designated as well by “gas lift”) may not allow to reduce sufficiently the hydrostatic pressure to operate the well in a satisfactory manner.
FIG. 1 shows a diagram of different characteristics of the productivity in relation with the fluid pressure in the well bottom hole and the flow rate, named Q. The fluid pressure of the well bottom hole is designated in FIG. 1 by the reference sign BHFP, abbreviation of “Bottom Hole Fluid Pressure”. FIG. 1 shows three characteristics 102, 112 and 122, of different wells. These wells are different by their gradient of natural lift, as defined by the following equation:
  Lg  =                    BHP        -        THP            H        *    10.2  wherein Lg is the gradient of the well natural lift;
BHP is the bottom hole pressure in bars (abbreviation of “Bottom Hole Pressure”)
THP is the wellhead pressure in bars (abbreviation of “Tubing Hanger Pressure”);
H is the vertical depth of the well in m.
The characteristics of curves 112 and 122 correspond thus to wells with an Lg lower than the well characteristic represented by the curve 102, Lg related to the well of the curve 122 being itself lower than the Lg related to the well of the curve 112.
Curves 104 and 114 of FIG. 1 correspond respectively to the performance of a gas lift called light and to the performance of a gas lift called heavy. The light gas lift has two operating points with the well of curve 102 whose point 106 allows a greater flow, Q, of well production. However, the light gas lift has no operating point with wells of lower Lg such as wells of curves 112 and 122. The low gas lift allows then the operation of wells with a Lg included between 0.6 and 1.0. The positioning of the heavy gas lift ensures then the operation of the well of curve 112 at an operating point 112 but does not allow to operate the well of curve 122 with which it has no operating point. The strong gas lift allows to operate wells with a Lg included between 0.3 and 0.5. In other words, the gas lift, even strong, is insufficient for operating the wells with a too low Lg.
There is therefore a need for a hydrocarbon production method and facility wherein activation by gas injection is insufficient to obtain a reduction of the hydrostatic pressure of the well allowing the operation of the well.
Therefore, the invention proposes a hydrocarbon production facility, comprising:                a well of hydrocarbons;        a hydrocarbon production line comprising:                    in the well, a production tube, and            on the surface, an evacuation tube from the production tube;                        on the surface, a source of pressurized gas;        an injection line of pressurized gas in the hydrocarbon production line, the injection line being connected to the source of pressurized gas;        a pump for circulation of hydrocarbon from the well to the hydrocarbon production line;        a pneumatic motor for supplying power to the pump, disposed on the injection line of the pressurized gas and adapted to be rotated by expansion of the pressurized gas.        
Alternatively, the facility comprises a mechanical transmission shaft connecting the pneumatic motor to the pump. Alternatively, the pneumatic motor is an electric generator. Alternatively, the pump in the well is an electric submersible type or a progressive cavity type. Alternatively, the pump is disposed in the well bottom hole.
Alternatively, the injection line opens into the well bottom hole, preferably in the production tube of the hydrocarbon production line. Alternatively, the pneumatic motor is at the wellhead. Alternatively, the pneumatic motor is at the well bottom hole. Alternatively, the injection line opens into the evacuation tube of the production line, downstream of the circulation pump.
The invention also provides a method of operating a hydrocarbon production well activated by gas injection, comprising:                a) providing pressurized gas from a source of pressurized gas surface;        b) recovering energy by the expansion of pressurized gas under pressure using a pneumatic motor;        c) actuating a pump for circulation of hydrocarbon from the well using energy recovered in step b);        d) injecting expanded pressurized gas in a hydrocarbon production line.        
Alternatively, pressurized gas is at a pressure higher than or equal to 70 bars prior to expansion. Alternatively, pressurized gas is expanded by the pneumatic motor at a pressure less than or equal to 30 bars.
The invention also concerns an upgrade method of a hydrocarbon production facility, the facility comprising:                a well of hydrocarbons;        a hydrocarbon production line comprising:                    in the well, a production tube, and            on the surface, an evacuation tube from the production tube;                        on the surface, a source of pressurized gas;        an injection line of pressurized gas in the hydrocarbon production line, the injection line being connected to the source of pressurized gas;        the method comprising:        positioning a pump for circulation of hydrocarbon from the well; and        positioning, on the injection line of pressurized gas, a pneumatic motor for supplying power to the pump, adapted to be rotated by expansion of the pressurized gas.        